This invention relates to an illumination device for a front panel such as those used in motor vehicles. More particularly, this invention relates to an illumination device for a front panel having illuminated areas which are illuminated through light guides placed behind the front panel and the light source being a lamp held in a connection base located behind the front panel.
Illumination devices of this kind are used, for example, in front panels whose illuminated areas serve as illumination or displays. Such front panels often have control elements. The illuminated areas can then indicate the particular setting of the control element. For example, such illumination devices are used in front panels in motor-vehicle control units, for example, in the ventilation or air-conditioning unit. They can also be used in consumer electronics devices. An example of such illumination devices may be found by reference to West German patent publication no. DE-OS 33 17 807.
In known illumination devices of the type mentioned, the lamp is difficult to remove when it becomes defective because it is located at an inaccessible point behind the front panel. It is therefore almost impossible for the user to replace the lamp in an easily accessible location, remote from the illuminated areas, since the light utilization of the lamp then decreases, and the lamp may cast stray light at undesired points.
The purpose of the invention is to recommend an illumination device of the above-mentioned type, in which the lamp is easily replaceable without opening or dismantiling the illumination device or the control unit, and its light is efficiently utilized,
According to the invention, the above purpose is fulfilled in an illumination device of the above-mentioned type by the fact that removably attached to the front panel is a cover member, beneath which the connection base is placed so that the lamp points away from the cover member, and that the lamp projects behind the front panel towards the light guides. By this means, after the cover member has been removed, the connection base and therefore the lamp as well, are easily accessible from the front panel. The lamp can therefore be easily replaced after the cover member has been removed. Because of the fact that the lamp extends from the base, placed in front, back towards the light guides, its light is emitted fairly directly towards the later, producing good light utilization, particularly if sufficient free space is available in the area behind the front side to allow optimization of the arrangement of the light guides. This arrangement additionally means that the lamp does not emit undesired stray light towards the front, which would have to be blocked off using special measures.
To prevent connection wires from being drawn out when the base is removed, a preferred embodiment of the invention provides for a contact device between the connection base and the electrical connection which disconnects when the connection base is removed. For this purpose, it is possible to provide, for example, a plug connection or another simple arrangement of contact springs.
The connection base can be placed on the front panel or base plate independent of the cover member. The result is that after removal of the cover member, the connection base must be removed separately. To circumvent this, according to one embodiment of the invention, the connection base is attached to the cover member. After removal of the cover member, the lamp is then directly accessible.
In one further development of the invention, the cover member is configured as a control part, e.g. a rotary knob. The result is that in the case of front panels on which control parts are provided in any event, an additional cover member and its attachment to the front panel are superfluous. The connection base and the lamp are then covered by the control part itself or one of the control parts themselves. In this case, it is recommended that the contact device consist of wiper contacts on the connection base and annular strip conductors on the electrical connectors.
To illuminate the control part and also make its position recognizable in the dark, it is preferable to place in the control part an additional light guide which ends in the region of the surface of the control part and is illuminated by the lamp. With this arrangement, it is advantageous for the connection base to be made of a transparent material and to be formed onto the light guide as a single piece.